Evaluation of transgenic, Bt-containing corn hybrids

European corn borer [ECB; Ostrinia nubilalis (Hubner]) is a major economic pest of corn (Zea mays L.) throughout the Corn Belt. Transgenic corn hybrids containing a modified Bacillus thuringiensis (Bt) gene were evaluated at four Corn Belt environments as a novel method of managing ECB. Manual infestation was done to insure the presence of ECB, and Bt-based insecticides were used to control natural infestations. First generation ECB damage, estimated by leaf damage ratings, and second generation ECB damage, estimated by amount of stalk tunneling, were reduced or eliminated with the use of the Bt hybrids. Grain yield, stalk lodging, and test weight of the transgenic hybrids were not affected by first or second generation ECB infestation. Grain yields of sir nontransgenic hybrids were not affected by first generation ECB infestation, but second generation ECB infestation damage, even though relatively low in the environments tested, reduced grain yield in these hybrids by 4.0 to 6.6%, slightly increased stalk lodging, and slightly decreased test weight. In the absence of ECB pressure, the transgenic hybrids performed the same as their nontransgenic counterparts. It is clear that the incorporation of the Bt gene into corn hybrids provides a high level of protection against ECB, with little if any effect on agronomic performance.